The ram-air gliding parachute is known. It consists of a flexible canopy of generally airfoil shape which is inflated and sustained by air flow into cells constructed in the canopy. See, for example, any of the following patents which relate to this type of parachute: 3,285,546; 3,524,613; 3,724,789; 3,972,495; 4,129,272; 4,191,349; 4,389,031 and 4,406,433.
Control of the gliding parachute's forward velocity is a point of concern on landing because of high forward speeds attained by the parachute. An early means of effecting control was to vary the canopy shape through the load lines in general and the front central lines in particular, in order to regulate the forward (and downward components of) glide speed during descent. This type of control, which can be referred to as airfoil distortion control, is not entirely acceptable both because of the necessity to recover from a possible stall condition, and an inherent inefficiency in the method.
Subsequently control has been obtained by bringing the trailing-edge of the canopy downward into a rear flaps configuration by the use of brake lines. As these flaps are pulled downward into effect changing the canopy angle of attack, they raise the lift coefficient of the canopy and thus exchange forward speed for lift. Doing this properly and rapidly ("flaring") converts momentum to lift, thereby reducing descent velocities by a factor of 15 or 20 for landing. This rear-flap "flaring" is quite effective for ram-air parachutes with small aspect-ratios as well as untapered ram-air parachutes, i.e., those with equal chord length along the entire span of the wing. However, for ram-air parachutes of higher aspect-ratios, for example, aspect-ratios of 2.8 and greater, and/or for tapered parachutes, the rear flaps are not sufficient to transfer momentum into lift to slow the canopy down to a desirable horizontal and vertical landing velocity. The use of rear flaps, while adding lift and increasing the maximum lift coefficient, do not sufficiently increase the angle of attack at which stall occurs.